JP2008110306A - Membrane module, water treating apparatus and membrane separation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the filtration flow rate of a membrane module to a prescribed value for a long period and to secure the stable operation of the membrane module by suppressing the clinging of foreign substances to the hollow fibers of the membrane module and preventing the falling down of hollow fiber bundle comprising the hollow fibers. <P>SOLUTION: The membrane module 1 is provided with the hollow fiber bundle 11 comprising a plurality of the hollow fibers being in contact with water to be treated. In the hollow fiber bundle 11, the upper end is a fixed end and the lower end is a free end. The hollow fiber bundle 11 is arranged in the downward stream. A fixing part for fixing the upper end of the hollow fiber bundle 11 to be the fixed end is preferably connected to a pipe for introducing air for scrubbing the hollow fiber 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hollow fiber type membrane module applied to a membrane separation activated sludge method, a water treatment apparatus equipped with the same, and a membrane separation system.

  FIG. 6 is a flow diagram showing a configuration example of a water treatment apparatus (hereinafter referred to as an MBR process) to which the membrane separation activated sludge method is applied. FIG. 7A is a plan view of a hollow fiber membrane module (hereinafter referred to as a membrane module) applied to the MBR process. FIG. 7B is a cross-sectional view showing a schematic configuration of the membrane module applied to the MBR process.

  Sewage supplied to the MBR process 6 is introduced into the raw water tank 62 through a screen dust remover (1 mm) 61. The sewage in the raw water tank 62 is supplied to the biological reaction tank 63 by the pump P1. The biological reaction tank 63 includes an oxygen-free tank 64 and an aerobic tank 65. The anaerobic tank 64 mainly performs a denitrification process. An underwater stirrer M is installed in the anoxic tank 64. The aerobic tank 65 mainly performs nitrification treatment. A diffuser 66 and a membrane module 67 are installed in the aerobic tank 65. The air diffuser 66 is supplied with air from the aeration blower B1. The liquid phase in the aerobic tank 65 is sucked by the pump P2, introduced from the outside to the inside of the hollow fiber membrane of the membrane module 67, and filtered. The filtered sewage is transferred to the discharge tank 68. The above MBR process is exemplified in Non-Patent Document 1.

  An example of the membrane module 67 is a hollow fiber type membrane module disclosed in Patent Document 1. The membrane module 7 illustrated in FIGS. 7A and 7B is similar to the hollow fiber membrane module of Patent Document 1. The membrane module 7 is configured by housing a hollow fiber bundle 72 composed of a plurality of hollow fibers 71 in a cylindrical outer cylinder 73. The hollow fiber bundle 72 is fixed by an upper cap 74 and a lower cap 75 installed at the upper end and the lower end of the outer cylinder 73, respectively. The upper cap 74 is connected to the outer cylinder 73 coaxially by a connecting portion 77. The lower cap 75 is also connected to the outer cylinder 73 coaxially by a connection part 77 (not shown). The raw water flowing in from the upper and lower openings of the outer cylinder 73 is filtered by the hollow fiber 71. The filtered water is discharged from the filtered water suction pipe 76 connected to the upper cap 74.

  Since the membrane module 7 introduces raw water (liquid phase in the aerobic tank 63 in the MBR process of FIG. 6) from the outside of the hollow fiber 71, organic or inorganic substances adhere to the outside of the hollow fiber membrane over time. Then it closes. Therefore, the filtration capacity decreases with time. In order to prevent a decrease in filtration capacity, the following measures are usually taken.

  (1) During the filtration time, scrubbing is performed by supplying air from an air diffuser 671 installed at the bottom of the membrane module 67, raising bubbles of a relatively large diameter, and shaking the hollow fiber membrane (see Patent Document 1). . The air is supplied from the membrane cleaning blower B2.

  (2) Backwashing is performed using filtered water for a fixed time interval (for example, 30 seconds out of 10 minutes).

  (3) A cleaning solution such as a sodium hypochlorite solution is supplied from the cleaning solution tank 69 into the hollow fiber of the membrane module 67 by a pump P3 at regular intervals (for example, once a month) to perform chemical cleaning.

  (4) Hollow fibers that are transferred to a cleaning liquid tank in which cleaning water containing sodium hypochlorite liquid or the like is stored every predetermined period (for example, once a year) and immersed in the cleaning water for a predetermined time, for example, one day or night The deposit on the film is removed.

(5) A fine screen is provided in front of the biological reaction tank 63 in order to prevent entanglement of fibers, hair, etc. and damage of the hollow fiber membrane due to foreign substances.
41st Sewerage Research Presentation Lecture pp. 762 (2004) JP 06-039249

  However, even if a fine screen is provided, it is difficult to remove all fibrous impurities such as hair. Therefore, when the MBR process is operated for a long period of time, fibrous contaminants are gradually entangled with the hollow fiber and gathered on the upper part of the membrane module 67 due to an upward flow caused by scrubbing bubbles. Furthermore, microbial membranes and other contaminants adhere and grow using the entangled fibrous contaminants as the core. When such adhesion occurs, the filtration efficiency of the adhered part decreases. Further, when the adhesion increases, the filtration capacity of the membrane module 67 also decreases. In addition, this increase in adhesion becomes a factor in cutting the hollow fiber. Such deposits cannot be removed by the above-described backwashing (2) or chemical solution backwashing (3), and the membrane module 67 is removed from the washing solution tank and removed manually.

  Therefore, the adhesion phenomenon of the foreign matter lowers the filtration efficiency and requires complicated maintenance work. Therefore, it must be solved for long-time operation. Further, unmanned operation is required for MBR applied to a small-scale water treatment facility, and the solution of the adhesion phenomenon is essential.

  As a method of preventing this adhesion phenomenon, a structure in which the hollow fiber is made free at the upper end of the membrane module 67 and the raised fibrous contaminants slip through the upper end of the hollow fiber can be considered, but at present, the upper end of the hollow fiber is free. If it is at the end, the hollow fiber cannot be made to stand by itself, and a situation occurs such that the hollow fiber falls during filtration operation or backwashing. This leads to breakage of the hollow fiber.

  Therefore, the membrane module of the present invention includes a hollow fiber bundle composed of a plurality of hollow fibers in contact with the water to be treated, and the hollow fiber bundle has a fixed end at the upper end and a free end at the lower end. Yes. The hollow fiber bundle is subjected to a downward flow of the water to be treated.

  The water treatment apparatus of the present invention is a water treatment apparatus comprising an anaerobic tank and an aerobic tank, a membrane module that performs a solid-liquid separation process on the sludge mixed liquid in the aerobic tank, and a membrane in which the membrane module is installed A filtration tank and a pump for returning the sludge mixed liquid in the membrane filtration tank to the oxygen-free tank are provided. The membrane module includes a hollow fiber bundle composed of a plurality of hollow fibers in contact with the sludge mixed solution. The hollow fiber bundle has a fixed end at the upper end and a free end at the lower end. Further, the hollow fiber bundle is used for the downward flow of the sludge mixed liquid generated by returning the sludge mixed liquid.

  The membrane separation system of the present invention includes a water channel to which a sludge mixed solution in an aerobic tank is supplied and a membrane module that performs a solid-liquid separation process on the sludge mixed solution flowing through the water channel. The water channel is disposed higher than the aerobic tank and is installed perpendicular to the liquid level of the aerobic tank so that the sludge mixed liquid flows down to the aerobic tank. The membrane module includes a hollow fiber bundle composed of a plurality of hollow fibers in contact with the sludge mixed solution. The hollow fiber bundle has a fixed end at the upper end and a free end at the lower end. The hollow fiber bundle is used for the downward flow of the sludge mixed liquid generated in the water channel.

  According to the above invention, the lower end of the hollow fiber is a free end, and the hollow fiber is provided for the downward flow of the liquid phase to be treated (water to be treated and sludge mixed liquid), thereby preventing entanglement of fibrous impurities. The fall of the hollow fiber can be prevented. In addition, since the entanglement of the contaminants is prevented, the adhesion of organic matter or the like with the contaminants as a core is also suppressed. Therefore, long-term maintenance of the predetermined filtration flow rate and stable operation are ensured.

  Further, in the membrane module, a pipe for introducing air for scrubbing the hollow fiber may be connected to a fixing portion having the upper end of the hollow fiber bundle as a fixed end. According to this, the scrubbing air can be self-supplied and the scrubbing bubbles generated by the introduction of the air come into contact with the sludge mixed liquid for a relatively long time while shaking the hollow fiber. The oxygen supply energy is reduced.

  As a form of circulating supply of the sludge mixed liquid in the membrane separation system, there is one provided with a tank that receives the sludge mixed liquid discharged from the water channel and returns it to the aerobic tank by overflow. According to such a form, the sludge liquid mixture of an aerobic tank can be stably circulated and supplied with respect to the said membrane module. The sludge mixed solution can be stably circulated and supplied when the lower end of the water channel is arranged so as to infiltrate a predetermined length below the liquid level of the tank. As another form of circulating supply of the sludge mixed liquid, there is one provided with a tank for supplying the sludge mixed liquid introduced by overflow from the aerobic tank to the water channel. Even in such a form, the sludge mixed liquid can be stably circulated and supplied to the membrane module. When the water channel is arranged so that the lower end of the water channel enters under the liquid surface of the aerobic tank, the sludge mixed solution can be circulated and supplied stably.

  In addition, the membrane module of this invention is applicable not only to the membrane module used for the membrane separation activated sludge method of a wastewater treatment, but to the immersion filtration membrane module etc. in a water purification process.

  According to the above invention, it is possible to prevent entanglement of fibrous impurities and to prevent the hollow fiber from collapsing. In addition, since the entanglement of the contaminants can be prevented, adhesion of organic matters and the like with the contaminants as a core can also be prevented. This ensures long-term maintenance of the predetermined filtration flow rate and stable operation. This also leads to a reduction in maintenance and inspection work for facilities equipped with membrane modules.

  Fig.1 (a) is a top view of the membrane module which concerns on 1st embodiment of invention. FIG. 1B is a side view showing a schematic configuration of the membrane module.

  The membrane module 1 includes a hollow fiber bundle 11. The hollow fiber bundle 11 includes a plurality of hollow fibers 12. The membrane module 1 does not include a lower cap part. That is, the hollow fiber bundle 11 is only held by the upper cap portion 13, and the lower end of the hollow fiber bundle 11 is a free end. The lower ends of the individual hollow fibers 12 are sealed. A filtered water suction tube 14 is connected to the upper end of the upper cap 13 substantially coaxially with the hollow fiber bundle 11. The filtered water suction pipe 14 is a discharge port for sucking filtered water supplied from the inside of each hollow fiber 12 of the hollow fiber bundle 11 by a pump not shown and transferring it to the outside of the system (for example, a discharge tank). .

  The membrane module 1 is immersed in the liquid phase (water to be treated) in which the downward flow is generated, and fibrous impurities existing in the vicinity of the hollow fiber 12 in the liquid phase are excluded from the nearby region by the downward flow. It has come to be. Thereby, the entanglement of the impurities on the hollow fiber 12 is suppressed. Further, since the hollow fiber bundle 11 is provided for the downward flow of the liquid phase, it is maintained in an almost upright state during the filtration process to prevent the collapse. In the membrane module 1, since the upper end of the hollow fiber bundle 11 is a fixed end, the maintenance inspection can be performed reliably without the hollow fiber 12 falling down even when taken out from the liquid phase to be treated.

  FIG. 2 is a schematic view of a water treatment device 2 to which the membrane module 1 is applied.

  The water treatment apparatus 2 includes an oxygen-free tank 21, an aerobic tank 22, and a membrane filtration tank 23. The anoxic tank 21 is denitrified by the raw water introduced by the raw water pump P21 and the sludge mixed solution returned by the pump P23. The aerobic tank 22 nitrifies the sludge mixed solution overflowed from the anoxic tank 21. The aerobic tank 22 includes an air diffuser 24 for introducing air necessary for nitrification into the tank. The air is supplied from the blower B. The membrane filtration tank 23 includes the membrane module 1 in the tank. The sludge mixed solution in the membrane filtration tank 23 is quantitatively returned to the anoxic tank 21 by the pump P23. In the case where the oxygen-free tank 21 is not provided, it may be supplied cyclically from the filtration membrane tank 23 to the aerobic tank 22.

  An operation example of the water treatment apparatus 2 will be described with reference to FIG.

  The sludge mixed liquid flowing into the membrane filtration tank 23 by overflow from the aerobic tank 22 is subjected to solid-liquid separation processing by the membrane module 1. The filtered water is sucked by the pump P22 and transferred from the filtered water suction pipe 14 to the outside of the system. A downward flow is formed in the liquid phase of the membrane filtration tank 23. The downward flow is formed by circulating the liquid phase in the membrane filtration tank 23 to the oxygen-free tank 21 by the pump P23. In the membrane module 1, entanglement of impurities contained in the sludge mixed liquid is suppressed by the downward flow. Further, when the sludge mixed liquid in the membrane filtration tank 23 is pulled out, the hollow fiber bundle 11 is fixed without falling down, so the membrane filtration tank 23 is filled with a cleaning chemical such as sodium hypochlorite (however, If the cleaning chemical solution is not transferred to the aerobic tank 21, the step of immersing and cleaning the membrane module 1 can be automated. By automating the cleaning of the membrane module 1, the operation of a small-scale facility equipped with the membrane module 1 can be unmanned, and labor saving can be realized in medium-scale and large-scale facilities.

  FIG. 3 is a side view showing a schematic configuration of the membrane module according to the second embodiment of the invention.

  The membrane module 3 includes an air introduction pipe 15 as a pipe for introducing scrubbing air into the upper cap portion 13. The scrubbing air is lowered by the suction force of the downflow of the liquid phase immersed in the membrane module 3. When the membrane module 3 is installed in the membrane filtration tank 23 of the water treatment device 2, the flow rate of the liquid phase in the membrane filtration tank 23 exceeds the rising speed of the scrubbing bubbles generated by the introduction of the air, so that the scrubbing bubbles A downward flow of a descending degree is formed in the liquid phase. This can be realized by appropriately designing the cross-sectional area of the filtration flow rate, the circulating sludge flow rate, and the amount of scrubbing air.

  FIG. 4 is a schematic view of a membrane separation system to which the membrane module 3 is applied.

  The membrane separation system 4 includes an aerobic tank 41, an elevated water tank 42, a vertical water channel 43, and a water receiving tank 44. The elevated water tank 42 is disposed higher than the aerobic tank 41. A vertical water channel 43 is connected perpendicularly to the liquid surface of the aerobic tank 41 at the bottom of the elevated water tank 42. The membrane module 3 is accommodated in the vertical water channel 43. The membrane module 3 performs a solid-liquid separation process on the sludge mixed solution provided from the elevated water tank 42. The water receiving tank 44 is disposed on the lower end side of the vertical water channel 43. The water receiving tank 44 is arranged so that the lower end of the elevated water tank 42 is slightly submerged below the liquid level. The water receiving tank 44 is adjusted so that an overflow weir is appropriately provided and the liquid level is kept substantially constant. The sludge mixed solution in the water receiving tank 44 is returned to the aerobic tank 41 by the overflow weir.

  An example of the operation of the membrane separation system 4 will be described with reference to FIG.

  The sludge mixed liquid in the aerobic tank 41 is transferred to the elevated water tank 42 by the pump P41. The sludge mixed liquid introduced into the elevated water tank 42 moves to the vertical water channel 43. The sludge mixed liquid introduced into the vertical water channel 43 is subjected to solid-liquid separation processing by the membrane module 1. In the membrane module 1, the entanglement of impurities contained in the sludge mixed liquid is suppressed by the downward flow of the sludge mixed liquid generated in the vertical water channel 43. The filtered water is sucked by the pump P42 and transferred from the filtered water suction pipe 14 to the outside of the system. On the other hand, scrubbing air is introduced from the air introduction tube 15 of the membrane module 1. The sludge mixed liquid discharged from the vertical water channel 43 stays in the water receiving tank 44 and then moves to the aerobic tank 41 by overflow.

  In the membrane separation system 4, the amount of water supplied to the elevated water tank 42, the inner diameter of the vertical water channel 43, the length of infiltration under the liquid surface of the water receiving tank 44, and the like are adjusted as appropriate. By this adjustment, a downward flow is formed in the liquid phase such that the flow rate of the sludge mixed liquid in the vertical water channel 43 exceeds the rising speed of the scrubbing bubbles generated by the introduction of the air and the scrubbing bubbles are lowered. Since the sludge mixed liquid is in a falling flow, the membrane module 3 uses the flow velocity of the falling flow to supply the scrubbing air from the air introduction pipe 15 shown in FIG. In addition, since the scrubbing bubbles in the vertical water channel 43 can contact the sludge mixed solution for a relatively long time while shaking the hollow fiber 12 of the membrane module 3, the action of supplying oxygen to the aerobic tank 41 is enhanced.

  FIG. 5 is a schematic view of another membrane separation system to which the membrane module 3 is applied.

  The membrane separation system 5 includes a supply tank 51 instead of the water receiving tank 44 in the configuration of the membrane separation system 4. The vertical water channel 43 is arranged so that the lower end thereof is slightly submerged below the liquid surface of the aerobic tank 41. The sludge mixed liquid is supplied to the elevated water tank 42 from the supply tank 51. The aerobic tank 41 is adjusted by providing an overflow or the like for transferring the sludge mixed liquid to the supply tank 51 so that the liquid level of the sludge mixed liquid is kept substantially constant. However, in this embodiment, a level meter that detects the liquid level in the supply tank 51 is installed, and it is necessary to control the operation of the pump P41 based on the detected liquid level. The set number of the membrane modules 1 and 3 and the vertical water channel 43 is not limited to the embodiment shown in FIG. 2, FIG. 4 and FIG.

  An example of the operation of the membrane separation system 5 will be described with reference to FIG.

  The sludge mixed liquid in the supply tank 51 is transferred to the elevated water tank 42 by the pump P41. The sludge mixed liquid introduced into the elevated water tank 42 moves to the vertical water channel 43. The sludge mixed liquid introduced into the vertical water channel 43 is subjected to solid-liquid separation processing by the membrane module 3. In the membrane module 3, entanglement of impurities contained in the sludge mixed liquid is suppressed by the downward flow of the sludge mixed liquid generated in the vertical water channel 43. The filtered water is sucked by the pump P42 and transferred from the filtered water suction pipe 14 to the outside of the system. On the other hand, scrubbing air is introduced from the air introduction pipe 15 of the membrane module 3. The sludge mixed liquid discharged from the vertical water channel 43 stays in the aerobic tank 41 and then moves to the supply tank 51 due to overflow. In the membrane separation system 5 as well, the amount of water supplied to the elevated water tank 42, the inner diameter of the vertical water channel 43, the infiltration of the aerobic tank 41 under the liquid surface, and the like are appropriately adjusted, and the downward flow to the extent that the scrubbing bubbles descend is generated. 43 is formed in the liquid phase. Since the scrubbing bubbles can contact the sludge mixed solution for a relatively long time while shaking the hollow fiber 12 of the membrane module 3, the oxygen supplying action to the aerobic tank 41 is also enhanced.

(A) The top view of the membrane module which concerns on 1st embodiment of invention, (b) The side view which showed schematic structure of the said membrane module. 1 is a schematic view of a water treatment device to which a membrane module according to a first embodiment is applied. The side view which showed schematic structure of the membrane module which concerns on 2nd embodiment of invention. Schematic of the membrane separation system to which the membrane module which concerns on 2nd embodiment is applied. Schematic of the membrane separation system to which the membrane module which concerns on 2nd embodiment is applied. The flowchart which showed the example of a structure of the water treatment apparatus based on a membrane separation activated sludge method. (A) The top view of the membrane module applied to the water treatment apparatus based on a membrane separation activated sludge method, (b) Sectional drawing which showed schematic structure of the membrane module applied to the said water treatment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 3 ... Membrane module 2 ... Water treatment apparatus 4, 5 ... Membrane separation system 11 ... Hollow fiber bundle, 12 ... Hollow fiber, 13 ... Upper cap part, 14 ... Filtrated water suction pipe, 15 ... Air introduction pipe 21 ... None Oxygen tank, 22 ... Aerobic tank, 23 ... Membrane filtration tank, 24 ... Air diffuser, P21 to P23 ... Pump, B ... Blower 41 ... Aerobic tank, 42 ... Elevated water tank, 43 ... Vertical water channel, 44 ... Water receiving tank , P41, P42 ... Pump 51 ... Supply tank

Claims (8)

A hollow fiber bundle comprising a plurality of hollow fibers in contact with the water to be treated is provided.
The hollow fiber bundle has a fixed end at the top and a free end at the bottom,
The membrane module, wherein the hollow fiber bundle is subjected to a downward flow of the water to be treated. The membrane module according to claim 1, wherein a pipe for introducing air for scrubbing the hollow fiber is connected to a fixing portion having an upper end of the hollow fiber bundle as a fixed end. In a water treatment device equipped with an anaerobic tank and an aerobic tank,
A membrane module for solid-liquid separation treatment of the sludge mixture in the aerobic tank;
A membrane filtration tank in which this membrane module is installed;
A pump for returning the sludge mixed liquid in the membrane filtration tank to the anoxic tank,
The membrane module comprises a hollow fiber bundle consisting of a plurality of hollow fibers in contact with the sludge mixed solution,
The hollow fiber bundle has a fixed end at the top and a free end at the bottom,
The hollow fiber bundle is used for a downward flow of the sludge mixed liquid generated by returning the sludge mixed liquid. A water channel to which the sludge mixture of the aerobic tank is supplied;
A membrane module for solid-liquid separation treatment of the sludge mixed liquid flowing through the water channel,
The water channel is disposed higher than the aerobic tank and is installed perpendicular to the liquid level of the aerobic tank so that the sludge mixed liquid flows down to the aerobic tank,
The membrane module comprises a hollow fiber bundle consisting of a plurality of hollow fibers in contact with the sludge mixed solution,
The hollow fiber bundle has a fixed end at the top and a free end at the bottom,
The membrane separation system, wherein the hollow fiber bundle is used for a downward flow of the sludge mixed solution generated in the water channel.   5. The membrane separation system according to claim 4, further comprising a tank for receiving the sludge mixed liquid discharged from the water channel and returning it to the aerobic tank by overflow.   The membrane separation system according to claim 5, wherein the tank is disposed so that a lower end of the water channel enters under the liquid level.   5. The membrane separation system according to claim 4, further comprising a tank for supplying the sludge mixed liquid introduced from the aerobic tank by overflow to the water channel.   The membrane separation system according to claim 7, wherein the water channel is disposed so that a lower end of the water channel enters under a liquid surface of the aerobic tank.

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